[billmeek]

When taking sharp curves at speeds over 45, I noticed the 400 feels like it's skipping in very small increments. I've felt it a couple of times before but today on one curve it was very noticeable. There's plenty of tread left on the tires and the rear shock is set stiff. I seem to remember reading somewhere about this effect but can't locate the article. Anyone have a similar experience?

 

[Bleeder]

I have heard that a worn variator symptom is a feel as though the bike is "shifting gears" without the subsequent change in rpm's, but I wouldn't know for sure because I've never worn one out.




Peace.

 

[billmeek]

I don't think it has anything to do with the drivetrain. It feels like the rear tire is barely losing grip and jumping a small amount toward the outside of the turn.

 

[Randy]

Billmeek wrote

When taking sharp curves at speeds over 45, I noticed the 400 feels like it's skipping in very small increments. I've felt it a couple of times before but today on one curve it was very noticeable. There's plenty of tread left on the tires and the rear shock is set stiff.

Since you checked the tires for tread I guess you did not notice any cupping on the tire
There is a chance between your stiff shock and perhaps a little too much tire pressure you could get the effect you mention . You may want to try a different combination and see if it helps.

 

[Bleeder]

Bearings?



Peace.

 

[NormanB]

Hi Bill

I trust you have checked for mechanical looseness at the rear wheel assembly.

From a handling point of view it is best to have the shock at max.

Some 'vagueness' can however be attributable to the scooter swinging arm design. Must confess mine gets a tadge unsettled at 80 mph + if I am tackling a curve and meet crosswinds.

 

[pauljo]

Road surface bumpy or smooth?

Even though you've got tread left, examine the tires for an uneven wear pattern - especially at the point where you are transitioning into being leaned over. My V-Strom did that to me today, but I know that the rear tire has developed ridges just to the side of the middle portion (which is somewhat flattened from straight up riding). I know it's the tire. Plenty of tread left on the V-Strom Bridgestones, but I'm trashing them in a week or two due to the hinky wear pattern. Got a set of Dunlops in the garage waiting to go on.

The Burgman 650 was getting skittish in the front, due to a nasty wear pattern on the Bridgestone front tire. I tossed it, even though their was tread left when I got my front Pirelli. It felt like a different machine as soon as the Pirelli went on.

I do not like the way Bridgestone tires wear. Period. I won't run them anymore on either of my machines.

 

[billmeek]

Just checked the tires for any odd wear. No uneven wear is evident. No play in the rear wheel either. The road was very smooth. I guess it could be the 'vagueness' from the swing arm design Norman mentioned.

 

[pauljo]

Yep. Having the weight of the engine on the swingarm is not ideal for handling. The Silver Wing is particularly affected by that, with its 600cc twin sitting on the swingarm. As far as I know, the Burgman 650 is still the only current scoot with a frame-mounted engine. As long as it doesn't throw you off line, it probably could be categorized as just an annoyance. Part of the "character" of the 400.

 

[billmeek]

It's one part of the character I could do without. It is a bit alarming to feel like the rear of the bike is skipping when leaned well into a curve. It's possible it may not actually be skipping ... just some sort of swingarm sideways vibration that gives it that feel.

In researching the topic, I ran across a disturbing article. See the second article down :

http://www.voidstar.com/bff/mag16.html

 

[NormanB]

Yep. Having the weight of the engine on the swingarm is not ideal for handling. The Silver Wing is particularly affected by that, with its 600cc twin sitting on the swingarm. As far as I know, the Burgman 650 is still the only current scoot with a frame-mounted engine. As long as it doesn't throw you off line, it probably could be categorized as just an annoyance. Part of the "character" of the 400.

Well the TMax is another!

 

[NormanB]

In researching the topic, I ran across a disturbing article. See the second article down :

http://www.voidstar.com/bff/mag16.html

I think that was discussed on the Yahoo forums this summer. I think it may have happened last year though.

 

[pauljo]

Well the TMax is another!

Another what? Frame mounted engine?

Not that it matters here in the USA...

 

[billmeek]

Norman,

You happen to remember general consensus on what 'might' have happened? Did anyone else report a similar 'skipping'?

The effect I felt should not be enough to cause you to lose contol of the bike. It's only felt when you're really leaning into a turn. I actually expected to scrub the centerstand. :wink:

 

[NormanB]

Norman,

You happen to remember general consensus on what 'might' have happened? Did anyone else report a similar 'skipping'?

The effect I felt should not be enough to cause you to lose contol of the bike. It's only felt when you're really leaning into a turn. I actually expected to scrub the centerstand. :wink:

IIRC there was no definitive conclusion as to cause - just effect. I do not believe the chap was hammering it and witnesses said he just 'careered off the road'.

 

[lycheed]

Hey Norman - the man that never sleeps,

I've often heard the design that you are refering to as the "swing axle" design as opposed to "swing-arm" design. Perhaps there are a couple of terms going around for the traditional engine-on-swing arm design. "Swing axle" is also the term used to describe the crude independant rear suspension systems of some 1950s/60s sports cars, so maybe everyone is confused... :?

To my knowledge, the SivlerWing and the TMax both have their engines located in the frames, as opposed to on the swing arm like the European offerings, and other single cylinder big-scooters. People sometimes discount the SW from the engine-in-frame catagory because the position of the rubber mounted engine is rearward in the frame, and the swing arm pivots on the same axle as the crankshaft, whereas the TMax and the AN650's engines are centrally located (with the AN650's being by the far the furthest forward in the frame).

You are right that the engine-on-swing-arm design causes handling problems above 65mph, and thee would be very noticebale at 80mph plus. This is due to the high amount of unsprung weight that doesn't allow the suspension to adequately control the attutde of the motorcycle in highspeed bends. The frames used with these types of scooter also allow an amount of flex which attributes to the weave you have described when travelling at speed.

Yamaha have tried to counter tride to counter this with their new Majesty by producing a aluminium girder like frame for the all-new model this year, which will reduce the frame flex, and have fitted heavy duty rear suspension to delay the inevitable effects of the engine-on-swing-arm design.

For vehicles with top speeds of 85mph or so, I think the handling package is more than adequate, and I would go as far as saying that the engine-on-swing-arm design allows easy changes of direction at speeds below 70mph, especially at low speeds were the inherant low centre of gravity of this design means that it's almost impossible to drop these things. Similarly, beacuse the engine is located on the swing arm as opposed to in the frame a simple frame can be used allowing a low weight design. The all-new 2004 Forza (Reflex) weighs 171kg dry, with traditional lightweight tubular frame. The 2004 new Majesty 250 weighs 194kg. Both have 23bhp to play with.

From my rides on the Majesty 250 and 400, I'm not conviced that the slight increased rigidity is the result of more handling orinetated stock suspension than the new Forza, or due the frame. I rode a 2003 Forza/Reflex with Honda's optional sports suspenson rear shock kit and it had a similar feeling on winding roads.

Anyway, take it easy out there when grinding centrestand at 85mph! :wink:

 

[roy_ryall]

Bill, I do not recall my 400 having that problem in the curves until the tires needed replacing. The tires still had tread on the center of the tire, but they developed a difference in the height of rubber on either side of the tread slots on the outer sides on the tire tread. I would not call it cupping. You have to look closely to see it. The same thing occurred on my friends 400 tires.

Since this handling concern has not been reported by other 400 riders, I would suggest it may not be "part of the "character" of the 400".

As to the article, it contains a lot of spectuation on the cause of the accident.

I would continue to look for other explanations.

How miles miles do you have on your bike? When did it start?

 

[bechtoea]

The tires for the B400 are relatively inexpensive as far as scooter/motorcycle tires go. I would replace the back tire and see if that makes the symptom go away. Even the age and wear of the rubber itself could cause this, I would guess.

 

[30MuleTeam]

When taking sharp curves at speeds over 45,...

I don't know your riding experience but could the problem be that you are pushing the 400 to it's limits? Let's face it, the 400 is not designed as a high speed sport machine. It is more of a commuter/touring machine. I would guess that your riding skill has exceeded the abilities of the 400 or that you are seeking a riding experience that the 400 cannot provide in stock form.

 

[billmeek]

Roy,

I'll take a closer look at the tire this afternoon. See if it fits the description you gave. Without looking at the odometer, I think it's only about 2500 miles. I've noticed it a few times before over the past 1000 miles or so. At first I only thought it was my imagination. I really was sure yesterday. I never notice it on short curves or at lower speeds. It was very pronounced on the 180 degree curve.

Dennis,

I do push the 400 a bit hard at times. But it's such a fun bike ... it just begs to be ridden.